Typically, hydrocarbon extraction involves drilling a wellbore into an oil and/or gas containing subterranean formation. Hydrocarbon extraction is facilitated by a vast number of interconnected pore throats which form channels within the subterranean formation thereby allowing flows of oil and/or gas to the wellbore. The ease of hydrocarbon extraction is dependent upon characteristics of the subterranean formation such as resistivity flow and capillary pressure, both of which are highly dependent upon the number, size, and distribution of unblocked pore throats within the subterranean formation. A common problem encountered during typical oil and/or gas extraction, is the decrease of productivity resulting from the blockage of pore throats by: 1) water, commonly referred to as “water block”; and/or 2) condensed hydrocarbons, commonly referred to as “condensate block”.
Water block occurs in oil and gas wells when pore throats are blocked by an accumulation of water which may be result of filtrate water from drilling mud, cross flow of water from water-bearing zones, water from completion or workover operations, water from hydraulic fracturing, and water from emulsions. Condensate block occurs in gas wells when pore throats are blocked by an accumulation of liquid hydrocarbons which may be the result of oil-based drilling mud, hydrocarbon liquids used in workover operations, and the use of oil-based fracturing fluids.
Additionally, the pressure during the extraction of gas often drops below the dew point pressure of the gas causing the gas to condense into liquid hydrocarbons also resulting in condensate block. Water blocks and condensate blocks may occur together or independently, leading to a decrease in well productivity and, in certain instances, to complete halt in production.
One method for the prevention or remediation of water blocks and/or condensate blocks involves modifying the wettability of the rock within the subterranean formation wherein the rock is contacted by a wettability modifier such that the rock's wetability is modified from an initially oil or water wet state to an intermediate or gas wet state. Proposed wettability modifiers include non-polymeric and fluorinated polymers, both of which are disclosed by Panga et al., in U.S. Patent Application with Pub. No. 2007/0029085.
Unfortunately, previously disclosed non-polymeric surfactants are disadvantageous for use as wettability modifiers because they suffer from low durability and tend to be easily washed away, therefore requiring repeated treatments. Previously disclosed fluorinated polymers are also disadvantageous for use as wettability modifiers because: 1) they have a high average molecular weight, typically about 140,000 g/mol or above; and 2) they have perfluoro alkyl moieties which are C8 or longer. This combination of high molecular weight and long perfluoro alkyl moieties translates to a high fluorine content and higher costs.
It would be desirable to discover a fluorinated polymer which can act as a wettability modifier without the aforementioned disadvantages.